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Cell Biology Block 4 > Histology Of The Eye > Flashcards

Histology Of The Eye Flashcards

1
Q

3 layers of the eye from outer to inner

A

Fibrous tunic, vascular tunic/uvea, and retina

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2
Q
  1. 2 parts of the fibrous (outer) layer
  2. How much do each take up of this layer
  3. Location of each part
  4. Point where the 2 come together is called
  5. Are they transparent or opaque?
A
  1. Sclera and cornea
  2. Sclera is posterior 5/6; cornea is anterior 1/6
  3. Sclera is continuous in front with cornea; cornea bulges forward from the sclera
  4. Corneoscleral junction (limbus)
  5. Sclera is opaque; retina is transparent
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3
Q

Cornea:

  1. Does it have blood vessels?
  2. Where does it receive its sensory innervation from?
A
  1. No

2. Ophthalmic nerve

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4
Q

3 parts of the vascular layer from posterior to anterior

Most of the vascular layer is composed of which of the 3 parts

A

Choroid, ciliary body and iris

Choroid

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5
Q

Choroid:

  1. Immediately deep to __
  2. Has a capillary plexus/arteries and veins held together by?
A
  1. Sclera (lines inside of the sclera)

2. Connective tissue with abundant melanocytes

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6
Q

Ciliary body:

  1. Location
  2. Suspensory ligament of the lens connects what 2 things?
  3. Another name for the suspensory ligament
A
  1. Raised area in anterior part of vascular layer
  2. Lens and inwardly projecting angle of the ciliary body
  3. Ciliary zonule/zonular fibers
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7
Q

Ciliary muscle:

  1. What is its function
  2. When does the ciliary muscle contract?
  3. What does contraction do to the suspensory ligament/tension of ligament on lens
  4. Innervation
A
  1. Muscle of accommodation; helps maintain a clear visual image as gaze is shifted from distant to near point or vice versa
  2. When shifting gaze from distant to near point
  3. Relaxation of the ligament and reduced tension by ligament on lens
  4. Parasympathetic via oculomotor nerve
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8
Q

Contraction of the ciliary muscle has what affect on the following:

  1. Tension by suspensory ligament on the lens
  2. Lens curvature
  3. Refractive power, why?
A
  1. Decreases
  2. Increases (becomes thicker in anterioposterior direction-becomes rounder)
  3. Increases (for vision of close objects - opposite happens when shifting gaze from a near point to a distant one)
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9
Q

Ciliary processes:

  1. What are they
  2. Its epithelium secretes what, where?
A
  1. Internal projections of the ciliary body

2. Aqueous humor; fills space between cornea and lens

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10
Q

Iris:

  1. Contains which other part of the eye?
  2. 2 muscles here and what do they do?
A
  1. Pupil

2. Sphincter pupillae and dilator pupillae muscle; control pupil size

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11
Q

Sphincter pupillae muscle:

  1. Structure
  2. Function
  3. Innervation
A
  1. Formed by circular fibers surrounding margin of pupil
  2. Decreases pupil size
  3. Receives parasympathetic innervation via oculomotor nerve (same as ciliary muscle)
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12
Q

Dilator pupillae muscle:

  1. Structure/location
  2. Function
  3. Innervation
A
  1. Formed by fibers that radiate from pupillary margin toward outer circumference of iris]
  2. Increases pupil size
  3. Receives sympathetic innervation from superior cervical ganglion
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13
Q

What are the 2 parts of the retina?

One of them has 2 subsections, what are they

What separates the optic part and non visual part

A

Optic part and non visual (ciliary and iridial) part

Ora serrata

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14
Q

Optic part of retina:

  1. Anterior or posterior part?
  2. Covers?
  3. Contains? (4)
  4. Where does it end
A
  1. Posterior part
  2. Covers inner aspect of choroid
  3. Photoreceptors (rods/cones), 1st and 2nd order neurons of visual pathway, interneurons and supporting cells
  4. Ends anteriorly at the ora serrata (a short distance behind ciliary body)
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15
Q

Nonvisual (ciliary and iridial) part of retina:

  1. Anterior or posterior
  2. Lines? (2 things)
  3. Consists of ?
A
  1. Anterior (thin)
  2. Lines internal aspect of ciliary body and posterior surface of iris
  3. 2 layers of epithelial cells (no nervous elements)
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16
Q
  1. Anterior chamber is between __ and __
  2. Posterior chamber is between __ and __
  3. How do both chambers communicate with each other
  4. Both chambers contain
A
  1. Cornea and iris
  2. Iris anteriorly and lens and suspensory ligament of lens posteriorly
  3. Via the pupil
  4. Aqueous humor
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17
Q

Aqueous humor:

  1. Secreted by?
  2. Drained at?
  3. Drains into? (3)
A
  1. Epithelium of ciliary processes
  2. Irido-corneal angle
  3. Trabecular meshwork -> scleral venous sinus (canal of schlemm) -> small scleral veins
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18
Q
  1. What is glaucoma

2. What is it usually caused by

A
  1. Increased intraocular pressure due to excessive amount of aqueous humor
  2. Drainage obstruction
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19
Q

Vitreous chamber is located where?

What is it filled with

A

Posterior to lens and its suspensory ligament

Vitreous humor/body = transparent, jelly like material

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20
Q

When you are looking at distant objects, how is your lens, zonule, and ciliary muscle

Close objects?

A

Lens flattened, ciliary muscle relaxed, zonule taut

Lens rounded, ciliary muscle contracted, zonule relaxed

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21
Q

Sclera:

  1. Type of tissue is it consists of
  2. 2 functions (general)
A
  1. Mainly DICT with bundles of type 1 collagen

2. Protects more delicate structures and provides sites for muscle insertions

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22
Q

Cornea:

  1. Vascular / nerves?
  2. 5 layers of the cornea from anterior to posterior
A
  1. No vascular; rich nerve supply
  2. Corneal epithelium, anterior limiting (Bowmans) membrane, stroma (substantia propria), posterior limiting (Descemets) membrane, and corneal endothelium
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23
Q

Corneal epithelium:

  1. What type of epithelium?
  2. Function of its basal cells
  3. Where do its basal cells emerge from?
  4. Corneal epithelium becomes continuous with __ at the corneoscleral limbus
  5. Why is corneal cancer rare? (Even though it is constantly exposed to UV light)
A
  1. Nonkeratinized stratified squamous epithelium
  2. Renewal and repair of corneal surface (turnover time ~7 days)
  3. Stem cells in the corneoscleral limbus
  4. Conjunctival epithelium
  5. Nuclei of corneal epithelial cells have FERRITIN that protects DNA from UV light
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24
Q

Anterior limiting (Bowmans) membrane:

  1. Function
  2. Where does this membrane end
  3. Does it regenerate?
A
  1. Acts as a barrier to the spread of infections to the underlying stroma
  2. Ends abruptly at the corneoscleral limbus
  3. No, but remember corneal epithelium does
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25
Q

Stroma:

  1. Consists of?
  2. What feature of the stroma contributes to the transparency of the cornea
  3. Between collagen lamellae are __
  4. Ground substance contains __, function?
A
  1. 60 thin layers (lamellae) of parallel collagen fibrils
  2. The uniform, right angle layout of the collagen
  3. Keratocytes (fibroblast-like cells)
  4. Lumican (keratan sulfate proteoglycan) that regulates normal collagen fibril assembly
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26
Q

Posterior limiting (Descemets) membrane:

  1. This layer is __
  2. Does it regenerate?
  3. At corneoscleral junction, it becomes continuous with __
A
  1. The thick basement membrane of the corneal endothelium
  2. Yes, readily regenerates after injury
  3. Trabecular meshwork
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27
Q

Corneal endothelium:

  1. What type of epithelium
  2. Directly in contact with?
  3. What happens at this layer?
  4. Largely responsible for regulating __, why?
A
  1. Simple squamous
  2. Aqueous humor
  3. Basically all metabolic exchanges of the cornea (most metabolically active cells of the cornea)
  4. Regulates proper hydration state of corneal stroma to provide maximal transparency and optimal light refraction
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28
Q

Corneoscleral limbus:

  1. What happens to the corneal stroma at limbus?
  2. Descemets membrane and corneal endothelium are replaced by __; function?
A
  1. It becomes vascular and less well organized as collagen bundles merge with those of the sclera
  2. Trabecular meshwork (spaces of Fontana) - allow continuous drainage of aqueous humor from anterior chamber
29
Q

Choroid:

  1. Location
  2. Consists of?
  3. Contributes to provide?
A
  1. Located in posterior 2/3 of eye
  2. LCT that is well vascularized with numerous melanocytes
  3. Provides O2 and nutrients to outer parts of retina
30
Q

Bruchs membrane

  1. Another name for it?
  2. What is it ?
  3. What does it contain?
A
  1. Lamina vitrea
  2. Thin layer of ECM between choroid and retina
  3. Collagen and elastic fibers
31
Q

Location of the ciliary body

A

Expanded part of uvea that encircles the lens; anterior to choroid and posterior to iris

32
Q

Ciliary processes:

  1. Epithelium?
  2. Difference between the cells that directly cover the connective tissue vs cells in surface layer
A
  1. 2 layers of low columnar or cuboidal epithelial cells
  2. Directly covering CT contain melanin and are called pigmented epithelial cells; cells in surface layer lack melanin and are called non-pigmented epithelial cells
33
Q
  1. Pigmented and non-pigmented epithelial cells secrete?

2. Non-pigmented epithelial cells also produce? Location?

A
  1. Aqueous humor

2. Zonular fibers - extend from grooves between ciliary processes to capsule of lens, holding lens in place

34
Q

3 functions of aqueous humor

A

Helps maintain intraocular pressure, provides nutrients, and removes metabolites from avascular tissues of cornea and lens

35
Q

Iris:

  1. Location
  2. Anterior surface of iris is exposed to?
  3. Anterior surface of iris consists of ?
  4. Most of iris consists of?
  5. What determines eye color
A
  1. Most anterior part of uvea that partially covers lens
  2. Exposed to aqueous humor of anterior chamber
  3. Dense layer of fibroblasts and melanocytes with interdigitating processes (lacks an epithelial covering)
  4. Stroma of LCT with melanocytes and rich microvasculature
  5. Melanocytes in stroma
36
Q

Iris:

  1. Posterior surface is covered by?
  2. Why are epithelial cells of the posterior layer heavily pigmented?
  3. Epithelial cells of the anterior layer of posterior surface (facing iris stroma) are less heavily pigmented, and are __ cells, function?
A
  1. 2 layers of epithelial cells continuous with those covering ciliary processes
  2. To protects eyes interior from excess light
  3. Myoepithelial cells - extend contractile processes radially to form dilator pupillae muscle
37
Q

So why is the posterior chamber always easy to identify?

A

Because it is highly pigmented

38
Q

How would you be able to tell which side the pupil is on when looking at the anterior surface of the iris?

A

Pupil is on the side closer to the sphincter pupillae muscle

39
Q

Lens:

  1. Located immediately behind
  2. Function
  3. Derived from?
  4. Features of its structure? (4)
  5. 3 components of the lens
A
  1. Iris
  2. Focuses light on retina
  3. Invagination of surface ectoderm (lens vesicle)
  4. Transparent biconvex structure, 2nd most important refractive element of eye, avascular, and highly elastic
  5. Lens capsule, lens epithelium, and lens fibers
40
Q

Lens capsule:

  1. Composed of?
  2. Location
  3. Provides attachment for
  4. Represents basement membrane of ?
A
  1. Proteoglycans and type IV collagen
  2. Surrounds lens
  3. Zonular fibers
  4. Embryonic lens vesicle
41
Q

Lens epithelium:

  1. Type of epithelium
  2. Location
  3. Where is the equator of the lens?
  4. What happens at the equator of lens?
A
  1. Single layer of cuboidal cells
  2. Present only on anterior surface of the cell, located immediately under lens capsule
  3. Near attachment of zonular fibers
  4. Epithelial cells proliferate and give rise to cells that become lens fibers.
42
Q

Lens fibers:

  1. Develop from
  2. Structure
  3. What happens as they mature
A
  1. Lens epithelium
  2. Highly elongated and tightly packed cells that appear as thin, flattened structures
  3. Lose their nuclei and organelles and their cytoplasm becomes filled with crystallin proteins
43
Q

Explain the following disorders of the lens:

  1. Presbyopia
  2. Cataract
A
  1. Loss of lens elasticity that reduces its ability to focus on objects close to retina (older people needing reading glasses)
  2. Loss of transparency of lens
44
Q

Cataract:

  1. May be caused by?
  2. If it significantly impairs vision, can be corrected by?
A
  1. Conformational changes of crystallin proteins

2. Surgically by removing lens and replacing it with a plastic prothesis

45
Q

Vitreous body:

  1. Located?
  2. Composition?
  3. Function of hyalocytes
A
  1. Posterior to lens and zonular fibers
  2. Transparent, gel-like material that is 99% water with glycosaminoglycans, collagen fibrils, and hyalocytes
  3. Synthesize glycosaminoglycans and collagen fibrils
46
Q

What is hyaloid (Cloquet’s) canal?

Where does it run?

A

Remnant of pathway of hyaloid artery of developing eye

Runs through center of vitreous body from optic disc to posterior lens capsule

47
Q

Development of retina:

  1. How is it initiated
  2. What induces lens formation
  3. What does optic vesicle form next?
A
  1. With an outpocketing of prosencephalon (optic vesicle and stalk)
  2. Optic vesicle grows to contact surface ectoderm and induces it to form lens
  3. Optic cup with inner and outer layers and intraretinal space in between
48
Q
  1. Outer layer of optic vesicle forms?
  2. Inner layer of optic vesicle forms?
  3. What are the first 2 neurons of visual pathway

~next these 2 layers contact each other and intraretinal space is obliterated

A
  1. Pigment epithelium of the retina
  2. Neural layer of retina (contains receptors)
  3. Interneurons and glial cells
49
Q

What happens in a retinal detachment?

What does this cause?

What does this require for treatment?

A

Intraretinal space reappears as neural retina tears away from pigment epithelium

Photoreceptor cells lose access to metabolic support from choroid and retina pigment epithelium and eventually die

Laser surgery

50
Q

Optic stalk transforms into __, how?

A

Nerve fibers from neural retina fill optic stalk and transform it into optic nerve

51
Q

Where does the optic nerve begin?

A

At the optic disc

52
Q

Retina cell types:

  1. What are the first 2 neurons of visual pathway
  2. What are the 2 interneurons
  3. Supporting cells?
A
  1. Bipolar are first order neurons, ganglion cells are second order neurons
  2. Horizontal and amacrine cells
  3. Muller cells
53
Q

Layers of the retina (from external to internal)

  1. Pigment epithelium - what type of cells?
  2. Next is the layer of?
  3. Next is outer limiting membrane is formed by junctional complexes between?
  4. Next is outer nuclear layer which contains?
  5. Next is outer plexiform layer which has synaptic connections between what 3 cells?
A
  1. Single layer of pigmented cuboidal cells
  2. Layer of rods and cones
  3. Between rods/cones and muller cells
  4. Contains nuclei of rods and cones
  5. Photoreceptors, bipolar cells, and horizontal cells
54
Q

Layers of the retina (from external to internal) continued..

  1. Inner nuclear layer contains
  2. Inner plexiform layer has
  3. Ganglion cell layer contains
  4. Nerve fiber layer contains? What do these do?
  5. Inner limiting membrane has what 2 things
A
  1. Nuclei of bipolar, horizontal, amacrine, and muller cells
  2. Synaptic connections between bipolar, ganglion, and amacrine cells
  3. Cell bodies of ganglion cells
  4. Axons of ganglion cells which converge at optic disc to form optic nerve
  5. Basement membrane and processes of muller cells
55
Q

Capillaries fed by central artery of retina extend to what layer

Supplies nutrients/O2 to outer retinal layers from capillaries in __

A

Inner nuclear layer

Choroid

56
Q

Pigment epithelium

  1. Lies on what membrane?
  2. Has microvilli that surrounds?
  3. Its microvilli/apical cytoplasm contain?
  4. 4 functions of this external layer
A
  1. Bruchs membrane
  2. Tips of photoreceptors
  3. Melanin granules
  4. Absorbs light to prevent glare (along with uvea), blood-retinal barrier, restores photosensitivity, phagocytosis from adjacent photoreceptors
57
Q

Rod cells:

  1. Allow vision in what kind of light
  2. Composed of
  3. Contains rhodopsin, function?
  4. Old discs are displaced by new discs, what happens to old discs
A
  1. Low intensity light (in the dark)
  2. Composed of hundreds of discs stacked like coins
  3. Initiates visual sensation when stimulated by light
  4. Phagocytosed by pigment epithelium
58
Q
  1. Location of outer segment of rod

2. What is between outer and inner segment of rod/cone

A
  1. Surrounded by cell membrane of the rod

2. Connecting stalk

59
Q

Cones:

  1. More or less abundant than rods?
  2. Contains visual pigment iodopsin which does what?
  3. Are discs shed more frequently in rods or cones
  4. Inner segment contains?
A
  1. Less
  2. Have sensitivity to green, red, and blue light
  3. Rods
  4. Metabolic machinery that supports activity of the cell
60
Q
  1. What is colorblindness?

2. Why is it more common in males

A
  1. Missing/defective specific class of cones

2. Its X linked

61
Q

Optic disc:

  1. Location
  2. What happens here
A
  1. Posterior part of retina

2. Axons of ganglion cells converge to form optic nerve

62
Q
  1. Central artery and vein run in the center of the optic nerve, when does it divide into branches?
  2. Initially these branches are located where - where do they run to?
A
  1. When they reach optic disc

2. Initially between inner limiting membrane and vitreous body - move into inner layers of retina

63
Q

Fovea centralis:

  1. Location
  2. Contains rods or cones?
  3. What part of retina surrounds the fovea centralis?
A
  1. Opposite pupil and just lateral to optic disc
  2. Cones
  3. Macula lutea
64
Q

What makes the macula lutea appear yellow in color

A

Contains carotenoids

65
Q
  1. What 2 glands are associated with the eyelashes

2. What causes a sty (hordeolum)

A
  1. Sebaceous glands (glands of Zeis) and apocrine sweat glands (glands of Moll)
  2. Bacterial infection of these glands
66
Q

Tarsal (Meibomian) glands:

  1. Location?
  2. Function of its secretions
  3. What is chalazion and what is it caused by
A
  1. Embedded in tarsal plates; deep to conjunctiva on deep surface of eyeball
  2. Creates an oily layer on surface of tear film that retards evaporation of tears
  3. Painless cyst in the middle of the eyeball caused by blockage of tarsal gland
67
Q

Conjunctiva:

  1. Location
  2. Type of epithelium
  3. Type of cells
  4. Mucus secretions from conjunctiva are added where?
A
  1. Membrane that covers exposed, anterior portion of sclera and inner surface of eyelids
  2. Stratified columnar epithelium
  3. Has numerous small goblet cells
  4. To tear film that covers conjunctiva and cornea
68
Q

Lacrimal gland:

  1. Function
  2. Location
  3. Consists of what type of units?
  4. Location and function of its myoepithelial cells
A
  1. Secretes tears
  2. Upper, lateral corner of eyelid
  3. Tubulo-acinar secretory units (have secretory granules)
  4. Located below secretory cells within basal lamina, aid in release of tears

Cell Biology Block 4 (9 decks)

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